Phytochemical analysis of isoflavonoids using liquid chromatography coupled with tandem mass spectrometry

Isoflavonoids are the biologically active secondary metabolites of plants that are being used for several health promoting and restoring effects mediated through different pathways. Isoflavonoids are structurally similar to estrogens due to which also known as phytoestrogens and have shown potent estrogenic and anti-estrogenic activity. Association with large biological activity lead to the need of rapid, sensitive and precise quantitation of different isoflavonoids in different plant extracts, food materials and biological matrices as the biological activities mainly depends on the quantities and nature of isoflavonoids present in them. The characterisation, standardisation and quantification of herbal extracts or food products require techniques that are highly selective, sensitive and also provide mass measurement precisions and structural information. Liquid chromatography with tandem mass spectroscopy has made it possible to analyse and characterize several constituents and their metabolites in a single run along with high selectivity and sensitivity. In this review, we have summarised the application of LC-MS/MS for the identification and quantification of isoflavonoids reported for various plant extracts and food products along with their general extraction procedures and factors affecting extraction providing a view towards the conditions used for their analysis. The most suitable and widely acceptable extraction solvent system for the isoflavonoids is methanol or ethanol in combination with water ranging from 40 to 60 % organic solvent based on the type of tissues and the isoflavonoids to be extracted by different extraction techniques. ESI ionization with Q-TOF MS was the most useful detection system for the characterisation and quantification of the diverse isoflavonoids with molecular insights.